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A DD4T.net Implementation - IFieldSet Extension Methods

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In my previous post Model Builders, I was presenting a way to build strongly typed models starting from an DD4T IComponent object.

The little bit of code that I will be presenting today is a set of extension methods for the IFieldSet object, as seen in the code below:

    IFieldSet fields = component.Fields;
    IFieldSet metadataFields = component.MetadataFields;
    Device device = new Device(component)
    {
        Brief = fields.ResolveRichText("Brief"),

        Metadata = new Device.DeviceMetadata()
        {
            LegacyId = metadataFields.NumericValue("Legacy_Id"),
            ShortTitle = metadataFields.StringValue("Short_Title"),
            Products = metadataFields.KeywordValues("Products"),
            Status = metadataFields.KeywordValue("Status"),
            RelatedTools = ToolBuilder.Instance.Build(metadataFields.LinkedComponentValues("Related_Tools")),
            UpdateDate = metadataFields.DateTimeValue("Update_Date")
        }
    };


These extension methods make it extremely easy to read values from the field set, without having to make several extra checks like verifying for null values, checking if named field exists among the fields in the set. Moreover, the return values are empty string, 0, min date, etc. The idea is to stay away from null wherever possible. This will make life easier for the future, so we don't have to check for null before every call.

As such there are helper methods to read every kind of IField: string, numeric, date, Component Link and Keyword. Also for convenience, I added a helper method to resolve rich text values.

    public static string StringValue(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null ? string.Empty : StringValues(fieldSet, fieldName).FirstOrDefault<string>() ?? string.Empty;
    }


One nice feature of extension methods is that they can be called on 'null' objects. So even if the fieldSet is null, the extension method is still called, so we can perform the null check inside the extension method, rather than before calling it. The StringValue method returns either empty string if the original string fieldSet is empty, otherwise it delegates the call to StringValues, which returns an IList<string> values or empty list.

    public static IList<string> StringValues(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null || !fieldSet.ContainsKey(fieldName) ? new List<string>() : fieldSet[fieldName].Values;
    }


The StringValues method performs the actual checks for whether there is such named field in the set, and if so, it returns its string values.

All other methods are very similar:

    public static IList<DateTime> DateTimeValues(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null || !fieldSet.ContainsKey(fieldName) ? new List<DateTime>() : fieldSet[fieldName].DateTimeValues;
    }

    public static DateTime DateTimeValue(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null ? default(DateTime) : DateTimeValues(fieldSet, fieldName).FirstOrDefault<DateTime>();
    }

    public static IList<IFieldSet> EmbeddedValues(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null || !fieldSet.ContainsKey(fieldName) ? new List<IFieldSet>() : fieldSet[fieldName].EmbeddedValues;
    }

    public static IFieldSet EmbeddedValue(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null ? null : EmbeddedValues(fieldSet, fieldName).FirstOrDefault<IFieldSet>();
    }

    public static IList<IKeyword> KeywordValues(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null || !fieldSet.ContainsKey(fieldName) ? new List<IKeyword>() : fieldSet[fieldName].Keywords;
    }

    public static IKeyword KeywordValue(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null ? null : KeywordValues(fieldSet, fieldName).FirstOrDefault<IKeyword>();
    }

    public static IList<IComponent> LinkedComponentValues(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null || !fieldSet.ContainsKey(fieldName) ? new List<IComponent>() : fieldSet[fieldName].LinkedComponentValues;
    }

    public static IComponent LinkedComponentValue(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null ? null : LinkedComponentValues(fieldSet, fieldName).FirstOrDefault<IComponent>();
    }

    public static IList<double> NumericValues(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null || !fieldSet.ContainsKey(fieldName) ? new List<double>() : fieldSet[fieldName].NumericValues;
    }

    public static double NumericValue(this IFieldSet fieldSet, string fieldName)
    {
        return fieldSet == null ? 0 : NumericValues(fieldSet, fieldName).FirstOrDefault<double>();
    }


One method that stands out is the RichTextField extension method. This method makes use of DD4T's RichTextHelper:

    public static IList<string> ResolveRichTexts(this IFieldSet fieldSet, string fieldName)
    {
        return StringValues(fieldSet, fieldName).Select(x => x.ResolveRichText().ToString()).ToList();
    }

    public static string ResolveRichText(this IFieldSet fieldSet, string fieldName)
    {
        string value = StringValues(fieldSet, fieldName).FirstOrDefault<string>();
        return value == null ? null : value.ResolveRichText().ToString();
    }




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